An American woman was stabbed to death in Costa Rica in what investigators suspect was a sexually motivated attack, officials said Wednesday.

The new details in the heinous slaying of Carla Stefaniak, 36, of Miami came a day after a security guard at the hostel where she was staying during her last night in Costa Rica was arrested in connection with her death.

Stefaniak was killed in an apartment she was staying in the Costa Rican capital of San Jose, and her partially-nude body was found covered in dirt nearby, officials said at a news conference Wednesday.

Walter Espinoza, director of Costa Rica's Judicial Investigation Department said investigators found traces of blood throughout the apartment where they believe Stefaniak was killed. Officials said that a preliminary assessment indicated that the killer's motivation was sexual, but additional tests are being conducted to confirm that theory.

Stefaniak's badly decomposed body was identified Tuesday through fingerprints and dental records, officials said. An autopsy found that she was stabbed in the neck, that her neck was broken and that she suffered trauma to the head.

While Martinez has not been charged in Stefaniak's death, Espinoza called him "a suspect."

He said Martinez is from Nicaragua and has an "irregular" immigration record.

Stefaniak was last heard from on Nov. 27, the night before her 36th birthday, her family told ABC News. She traveled to Costa Rica on Thanksgiving Day to celebrate her birthday with her sister-in-law, April Burton, but decided to stay an extra day after Burton returned to Florida on Nov. 27, the family said.

Martinez lived in the room next to Stefaniak's at the hostel, officials said. He was arrested after testimony he gave investigators didn't match surveillance footage or other witness statements, Espinoza. Martinez had been in the country since June, Espinoza said.

The testimony from Martinez was "incompatible to reality," Espinoza said. Martinez was living in apartment No. 7, while Stefaniak was staying next door in apartment No. 8. Blood was discovered in her room.

While FaceTiming with a friend around 7:20 p.m. that night, Stefaniak told the friend that she was thirsty, according to the timeline. When he suggested that she boil some water, she told him that all she could find was a skillet and said that she was going to ask one of the security guards to buy her a bottle of water, since it was raining, the family told WFTS. It's unclear if she had contact with one of the security guards.

The owner of the hostel told Stefaniak's family that she had checked out with all her belongings at 5:10 a.m. on Nov. 28, according to the timeline provided to WFTS. Stefaniak's flight wasn't until 1:30 p.m. that day, and the family said it was unlikely she would check out early for no reason. There were no security cameras on the property to verify the hostel owner's claim, the family told WFTS.

An Uber driver who had driven Stefaniak from the airport to the hostel on Nov. 27 -- after she dropped Burton off for her flight and returned their rental car -- told the family she'd asked him to pick her up the next morning around 8:30 a.m. and take her to a shopping center, but she never showed up, according to the provided timeline.

That Uber driver also had taken Stefaniak on a city tour of San Jose after she checked into the hostel, the family told WFTS.